First steps

Richard Lauer, student and employee of William Harvey, already in 1669 drew attention to the fact that even a slight inclination of the operating table, where the animal has an extremely strong influence on the inflow of venous blood to the heart and therefore, the performance of the pumping heart. Lauer linked it with the voltage of the vascular wall: the higher the voltage, the lower the blood may flow from the upstream vessels down. The voltage of the vessel wall Lauer called tone, and the term is still widely spoken.
Observations Lauer is extremely important, as they allow to assess the degree of active voltage smooth muscles of arteries and veins, especially the small veins that are called capacitive, because they usually contain about 80 % of all blood mammal. Samples based on the experiences of Richard Lauer, has acquired today special significance: it is the most important criterion of fitness to overloading pilots, astronauts, athletes, the criterion of the state of cardiovascular system of patients, long confined disease to the bed.
Realizing that the blood pressure at the entrance of the atrium is very low (close to zero, and even below zero, if you count zero, the atmospheric pressure and the pressure in the arteries must be high; the problem of measuring the pressure in the vessels became interested in Steven Hales. It happened in 1733, when it was already known equation Torricelli: the rate of leakage of fluid from the vessel through the hole in his thin wall proportional to the square root of the product of depth of flooding openings on the acceleration of gravity and even at two. From here you can imagine how high blood pressure, if through the capillaries has several liters of blood per minute. Hales proceeded from the fact that the capillaries - the bottleneck of the circulatory system. (Much later it was established that the maximum flow resistance have prekapilliarnae vessels (arterioles, although geometrically minimum cross-sectional area has aorta 800 times less than the total cross section of capillaries.)
Hales wanted to measure, what arterial and venous pressure inherent in animals of different species. The measurement was great difficulties due to the lack of pressure gauges, pressure pulsations, blood coagulation, resistance of the animal. In addition, Hales understood that single measurement does not provide the basis for accurate conclusions (today we would say that it is statistically insignificant), and the need for repeated several animals. That is why experiments were to cost dearly for rural pastor Stepna Hales.
Here the Protocol is one of the first experiments (1733): "the 1st of December, I gave orders to tie a horse lying on its back. She was twelve hands growth and the age of about fourteen. She had a fistula on" the back of the neck. She was not particularly good, and not too well-fed. Exposing the left femoral artery in the distance three inches from the belly, I introduced the copper tube about one-sixth of an inch in diameter, to it through other tight-fitting copper tubes I have attached a glass tube about the same diameter length nine feet *. When was unleashed ligature on arteries, the blood rose in this tube 8 feet and 3 inches on the perpendicular above the level of the left ventricle of the heart. She had reached this height not immediately she rose instantly to approximately half this height and then gradually rise with each beat of the pulse 12, 8, 6, 4, .2, and sometimes one inch. When she reached full height, then began to rise and fall with each or after each blow for 2, 3 or 4 inches. Sometimes she fell to 12 or 14 inches and gave here for some time, such as fluctuations up and down with each stroke of the pulse, as in the>time, when it reached full height. She came back to after the last forty or fifty ripple".
Thus took place the first ever measurement of blood pressure. The same methods Hales identified and venous pressure. Pulse fluctuations in blood pressure were significantly the average, smoothed inertia three-meter column of blood.
In subsequent experiments Hales significantly improved its method using flexible connection manometer artery using goose trachea; it defended the fragile tube from damage when moving a strong animal. In these experiments were discovered, as you can see, not only pulse vibrations, but the slow waves of pressure in the arteries is very important for clinical research, but as a rule, are not taken into account by doctors.
Stun Hales measured pressure in the veins and arteries horses, sheep, dogs and got the figures close to the adopted today.
It is impossible not to admire the ingenuity Hales-experimenter who glass gauge own design, just prepodavala height measured pressure to develop flexible articulation of the vessel with manometer, despite the absence of rubber and plastic tubes, and found the correct starting point - the left ventricle. Knowing the value of cardiac output and blood pressure, Hales calculated the power developed by the heart alone. Passing through the vessels of the intestine of the dog solution brandy - and that in itself was an incredible display of experimental skills,- the pastor found that intestinal blood flow under the effect of alcohol decreases, and used this fact in his sermons. Hardly religion ever received such a serious scientific arguments in favor of sobriety. But much more important that Hales first time in history made the vascular perfusion. Finally, Hales - first physiologist, whose works are not published on the traditional Latin, and in his own language.
Research Hales received practical application much later. Today blood pressure is one of the most important indicators of health or disease, as the amount of blood flow. The work of Richard Lauer, too, can be fully appreciated only in our time. However, the same or almost the same can be said about all significant scientific research. About the sh thought in 1667 expressed Thomas Sprat, author of "the History of the Royal society: "If you persist in condemning all the tests, Except those that bring immediate benefit and help you immediately reap the benefits, let condemn and Providence of the Lord for what He has not created all times of the year, the time of harvest the fruits of the earth."
Words Sprat seem today even more than in the XVII century, because in smoke "information explosion" harder to distinguish between serious and prospective studies from thoughtless day under the flag of relevance. Science is at all times obliged to remain wise.